SiC (silicon carbide) has been expected as a material for next-generation semiconductor devices. SiC has excellent properties: bandgap which is three times as large; breakdown field strength which is about ten times as high; and thermal conductivity which is about three times as high, as compared with Si (silicon). The utilization of the characteristics can achieve semiconductor devices that are low in loss and able to operate at high temperatures.
As in MOSFETs (Metal Oxide Semiconductors) and IGBTs (Insulated Gate Bipolar Transistors), it is important to reduce the ON resistance in a semiconductor device including a MOS structure. One of the ways to reduce the ON resistance is to metallize a source region (emitter region) to reduce the parasitic resistance of the source region (emitter region).
In metallizing the source region (emitter region), the reduced barrier against electrons between the source region (emitter region) and a channel region in an ON state is required for the reduction in ON resistance. However, as compared with Si, SiC has a larger bandgap, and smaller potential energy (corresponding to electron affinity) measured from a vacuum level at the lower end of the conduction band. For this reason, there is considered to be no appropriate metallic materials which have such a work function that lowers the barrier between the source region (emitter region) and the channel region. Therefore, it is difficult to adopt a device structure with a source region (emitter region) metallized, as compared with cases of Si.